Graphene, which consists of one or more atomic layers of graphite, has attracted a tremendous interest in recent years due to its unique electron mobility and physical properties. The electrical properties of graphene are largely influenced by its grain size and by the atomic structure at the grain boundaries. Such effects are even more pronounced in a two dimensional crystal where minor defects can disrupt the crystal structure.
Existing methods for making graphene generally include exfoliation from highly oriented pyrolytic graphite, desorption of silicon from silicon carbide single crystals, and chemical vapor deposition from gaseous methane/hydrogen mixtures. These methods, however, have numerous limitations and generally fail to produce graphene films that are large in area and also have large single crystal grains. For example, exfoliation limits the size of graphene layers while desorption from silicon carbide forms 2- and 3-layer graphene. Although chemical vapor deposition from gaseous methane/hydrogen mixtures is widely used for large area monolayer graphene, typically only small polycrystalline grains have been reported.
Thus, there exists a need for alternative methods for large-scale synthesis of a graphene monolayer over large areas that is clean and highly ordered, i.e., with large single crystal grains. Moreover, there is a need to reduce defects in the formation of the graphene structure (e.g., heptagonal or pentagonal structures instead of the repeating hexagonal structures) while also increasing the grain size.
Additional aspects will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the aspects described below. The advantages described below will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive.